Machined Parts

Surface treatments such
as pyrolytic coatings should only be done on finished,
machined parts. Machining after treatment will expose the graphite substrate.

Purification

Suffix

-2 for semiconductor grades that end in the
number 1; and -1 for other grades (industrial)

Effect

Reduces impurities to 5 ppm or less as determined
by ash analysis

Summary

Unpurified POCO graphites have typical impurity
levels of about 1000 ppm, but they can have
up to 3000 ppm. The dominant impurity is vanadium,
with some iron, aluminum, calcium, nickel,
titanium, and silicon. Gaseous impurities do
not show up in ash tests, and may be present
in small amounts in purified materials

Physical Properties

Not affected

Application

Recommended after final machining

Densification

Suffix

-3 for semiconductor grades
that end in the number 1; and -1 for other
grades (industrial

Effect

Reduces open porosity by 80%

Summary

Graphite has tiny voids (pores),
which may link to the surface (open porosity),
or be isolated (closed porosity). Densification
partially fills the open pores with pure carbon,
reducing the average pore size and open porosity.
This produces a graphite with very low permeability

Physical Properties

Not affected

Application

Can be applied to bulk material

Does not affect dimensions

Pyrolytic Treatment

The treatment completely seals the surface of the graphite and reduces
particle generation in demanding environments. These materials resist attack by acids.

POCO produces a number of pyrolytic carbon treated materials marketed
under different trade names for semiconductor applications.
Each of these different materials is targeted at specific applications.

For industrial application, POCO produces a pyrolytic carbon treatment on AXF-5Q
and this material is designated as AXF-5QPyC.